<template>
  <div id="app">
    <div>
      <p>请选择你要购买的书籍</p>
      <ul>
        <li v-for="(item, index) in arr" :key="item.name">
          {{ item.name }} <button @click.prevent="buy(index)">买</button>
        </li>
      </ul>
      <table border="1" width="500" cellspacing="0">
        <tr>
          <th>序号</th>
          <th>书名</th>
          <th>单价</th>
          <th>数量</th>
          <th>合计</th>
        </tr>
        <tr v-for="(item, index) in arr" :key="index">
          <th>{{ index + 1 }}</th>
          <th>{{ item.name }}</th>
          <th>{{ item.price }}</th>
          <th>{{ item.count }}</th>
          <th>{{ item.price * item.count }}</th>
        </tr>
      </table>
      <p>总价格为:{{ total }}</p>
    </div>
  </div>
</template>

<script>
export default {
  data () {
    return {
      arr: [
        {
          name: '水浒传',
          price: 107,
          count: 0
        },
        {
          name: '西游记',
          price: 192,
          count: 0
        },
        {
          name: '三国演义',
          price: 219,
          count: 0
        },
        {
          name: '红楼梦',
          price: 178,
          count: 0
        }
      ]
    }
  },
  methods: {
    buy (i) {
      this.arr[i].count += 1
    }
  },
  computed: {
    total () {
      return this.arr.reduce((t, c) => t + c.price * c.count, 0)
    }
  }
}
</script>

<style></style>
